#container {
	width: 800px;
	height: 500px;
	background: rgba(0, 0, 0, .8); 
	position: relative;
}
.box {
	transition: all 2s ease;
	animation: toBig 2s infinite;
}
@keyframes toBig {
	0 {
		transform: scale(.5, .5);
		opacity: 0;
	}
	50% {
		transform: scale(5, 5);
		opacity: 1;
	}
	100% {
		transform: scale(1, 1);
		opacity: .5;
	}
}